1. Field of the Invention
This invention relates to power supplies and more particularly to a voltage regulator having an FET inverter stage and an improved driver circuit for that stage.
2. Prior Art
One type of switching regulator which is well known in the prior art employs a full bridge topology for the inverter switches, with each of the four switching devices being driven by an isolated signal. The user of MOSFETS for these main switches allows lower drive power, but due to the desirably fast switching speeds and unavoidably relatively large input capacitance, gate voltage ringing can be a problem. Moreover, power switching circuits are often driven by transformers to provide isolation for the high voltages at reasonable cost. These transformers introduce additional inductances that make control of gate voltage very difficult. Also, the use of transformer coupling between the driver and inverter stages is accompanied by the well-known problem of transformer core "walking", that is saturation of the core due to asymmetrical operation thereof. Prior art solutions to these problems include compromises between switching frequency and the cost of special magnetics designed to reduce voltage spikes, and anti-walkng schemes which reduce efficiency, increase cost, or carry with them resident problems of their own.